This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Railroad cars and certain types of trucks having pneumatic brake systems use flexible air hoses which extend between separate railroad cars or portions of a tractor-trailer assembly for operation of the pneumatic brake system. In such systems, the brake system is connected with a source of compressed air by a flexible tube or hose, which kept pressurized at about 8.4-10.5 kg/cm2 (120-150 psi).
Typically, air brake hoses are formed of a multi-layer construction, with inner and outer layers being formed of a material which resistant to the surrounding environment. In particular, the inner and outer layers are formed from a material which is not sensitive to stress cracking by zinc chloride, such as nylon 11 (polyundecanolactam) or nylon 12 (polydodecanolactam). The inner and outer layers are separated by an intermediate layer of woven or braided material, such as a polyester fiber, which acts as a reinforcement.
Often, for the outer layer, air brake hoses utilize ethylenepropylene-diene copolymer rubber compound plasticized with 4900 SUS napthenic process oil. Articles, such as air brake hoses, using such material become brittle, when exposed to temperatures below −65 deg F. (−54 deg C.) exhibit low temperature embrittlement, which leads to failure in articles formed of such materials.
Thus, there exists a need for combinations of materials which form articles, such as air brake hoses, having acceptable extreme low temperature flexibility, such need met at least in part, with the following disclosure.